Visual indicator assembly

ABSTRACT

A visual indicator assembly for use with an underwater mine system comprises a surface position marker (11) having a buoyancy device (23), the marker (11) being adapted to provide visual and/or audible indications on the surface that a mine has been &#34;fired&#34;. The assembly further comprises a support device (13) for supporting the marker (11) underwater and a severable coupling (37) which, when severed, releases the marker (11) to float to the surface. The assembly further comprises a release means selectively operable to sever the coupling (37) and to release the marker (11) to float to the surface.

The present invention relates to a visual indicator assembly for use inunderwater operations.

In particular the present invention relates to a visual indicatorassembly for use with a Stonefish Exercise Mine ("SEM") to provide avisual indication to surface vessels that the SEM has been "detonated".

The Royal Australian Navy acquired recently a number of SEMsmanufactured by Marconi Underwater Systems Limited for use in trainingexercises for mine detection and clearance. The SEM is a programmablemagnetic/acoustic/pressure influence ground mine which can be used indepths of water to 90 meters and is deployed at sea by lowering the mineonto the water by crane and then releasing it to sink uncontrolled tothe sea bed.

The SEM is capable of communicating through a ship-activated acousticsonar link within the frequency range of 12 kHz to 16 kHz. When "fired"a firing signal generated by the SEM is recorded via an in-waterreceiver/recorder towed behind an attendant vessel. The mine firingsignal is registered on a display in the ship's bridge to tell thecommanding officer that the mine has "detonated".

The limited availability and the cost of the towed recorder precludesthe fitting of this equipment to all ships which exercise with the SEM.Consequently, ships without the benefit of the in-water electronics mustrely upon receiving the results of the mine data transmission messagesfrom other ships. The delay in notifying the recipient, and other ships,that a critical mine encounter may have occurred causes a significantlack of realism and concern to participating ships and devalues thetraining exercise.

With the above in mind, an object of the present invention is to providea real time visual mine firing indicator which will indicate to allships in an exercise that a SEM has transmitted a detonation signal.

According to the present invention there is provided a visual indicatorassembly for use in underwater applications comprising:

(a) a surface position marker having a buoyancy means, the marker beingadapted to provide visual and/or audible indications on the surface;

(b) a support means for supporting the marker underwater;

(c) a severable coupling which, when severed, releases the marker tofloat to the surface; and

(d) a release means selectively operable to sever the coupling and torelease the marker to float to the surface.

It is preferred that the marker be adapted to provide visual indicationswhen it floats to the surface.

It is preferred particularly that the marker be adapted to providevisual and audible indications when it floats to the surface.

It is preferred that the marker comprise visual and/or audiblepyrotechnics components.

It is preferred that the marker comprises an ignition system for thevisual and/or audible pyrotechnics components.

It is preferred that the release means be responsive to a "fired" signalfrom a Stonefish Exercise Mine.

It is preferred particularly that the "fired" signal be a sonar signal.

It is preferred that the release means comprises a means for receivingand recognizing the "fired" signal.

It is preferred that the release means comprises an ejection means forapplying a tensile force between the marker and the support means tosever the coupling and to release the marker after the "fired" signalhas been recognised.

It is preferred that the marker houses the ejection means.

It is preferred particularly that the marker comprises a watertightcompartment and that the ejection means be located in the compartment.

It is preferred more particularly that the severable coupling couplestogether a forward section and a rear section of the marker.

With such an arrangement it is preferred that the ejection means beoperable to apply a force against a rear end of the forward section ofthe marker and that the rear section of the marker be retained by thesupport means.

It is preferred that the ejection means be adapted simultaneously toactuate the ignition system for the visual and/or audible pyrotechnicscomponents of the marker.

It is preferred that the visual indicator assembly further comprises adelay fuse to delay ignition of the ignition system for the visualand/or audible pyrotechnics components of the marker until the markerreaches the surface.

It is preferred that the visual indicator assembly comprises:

(a) a plurality of the markers; and

(b) a plurality of the severable couplings.

It is preferred that the release means be operable to sever thecouplings and to release the markers successively in a predeterminedsequence.

According to the present invention there is also provided, incombination, the visual indicator assembly described above connected toa Stonefish Exercise Mine.

The present invention is described hereinafter by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a perspective view in schematic form of the main components ofa preferred embodiment of a visual indicator assembly of the presentinvention connected to a Stonefish Exercise Mine in an operationalposition underwater; and

FIG. 2 is a section through the line 2--2 in FIG. 1 illustrating indetail a preferred embodiment of a marker of the visual indicatorassembly;

FIG. 3 is a section along the line 2--2 in FIG. 1 illustrating in detailanother preferred embodiment of a marker of the visual indicatorassembly; and

FIG. 4 is a section along the line 2--2 of FIG. 1 illustrating in detailanother preferred embodiment of a marker of the visual indicatorassembly.

FIG. 1 illustrates in schematic form a preferred embodiment of a visualindicator assembly 3 of the present invention connected by means of apolymeric inert umbilical cord 5 to a Stonefish Exercise Mine ("SEM") 7resting on the sea bed 9. The purpose of the visual indicator assembly 3is to provide an almost immediate visual/audible indication on thesurface that the SEM has been "fired".

The visual indicator assembly 3 comprises, six surface markers 11 (onlyone of which is shown in FIG. 1), and a support means in the form of acradle 13 which supports the markers 11 underwater. The visual indicatorassembly 3 further comprises a severable coupling 37 (FIGS. 2 to 4)associated with each marker 11 which, when severed, releases the markers11 to float to the surface, and a release means which is selectivelyoperable in response to "fired" signals from the SEM to sever thecouplings 37 and to release the markers 11 in a predetermined sequenceto allow the markers 11 to float to the surface.

The cradle 13 comprises a hollow PVC frame having a number of buoyantfoam liners (not shown) to ensure that the visual indicator assembly 3floats above the seabed and maintains the markers 11 in the preferredoperational upright position as shown in FIG. 1. The cradle 13 furthercomprises a circular array of six openings 15 which, as can best be seenin FIG. 2, define the locations for the markers 11.

The cradle 13 also has a central opening which receives a cylindricalwatertight container 17. A second cylindrical watertight container 19 islocated on top of the container 17.

The container 17 houses a range of electronics components (not shown)including, an inbuilt hydrophone, a safe arming switch, and electronicsmodules which define a part of the release means for severing thecouplings 37 associated with the markers 11 and thereby releasing themarkers 11 to float to the surface. As is described hereinafter, theother part of the release means is associated more closely with thecouplings 37.

The container 19 houses a disposable battery pack for powering theelectronics components in the container 17.

With reference to FIG. 2, the preferred embodiment of the marker 11shown in the figure comprises, an elongate hollow member 21 having aforward end 81 and a rear end 83, a nose closure cap 29 which closes theforward end 81, a base member 39 which extends into the rear end 83 andlocates the marker 11 in one of the openings 15 in the cradle 13, and aclosed cell foam collar 23 which encloses a forward section of thehollow member 21 and is shaped so that the marker 11 has a generallyspherical "head". It is noted that the base member 39 of the marker 11is retained in the cradle 13 by spring clips (not shown) or any othersuitable means.

The rear end 83 of the hollow member 21 comprises a downwardly dependingcylindrical skirt 44 which comprises a first part 43 and a widerdiameter second part 49.

The base member 39 comprises a cylindrical sleeve 47 which extends intothe rear end 83 of the hollow member 21 and engages the skirt 44. Thesleeve 47 comprises a first part 85 and a narrower diameter second part87. The diameters of the parts 43, 49 of the skirt 44 and the parts 85,87 of the sleeve 47 are selected so that there is substantial contactbetween the first part 43 of the skirt 44 and the second part 87 of thesleeve 47 and between the second part 49 of the skirt 44 and the firstpart 85 of the sleeve 47.

The base member 39 further comprises a body member 60 which extendsthrough the opening 15 and a flange 71 which is received in an annularrecess 73 in the cradle 63.

The hollow member 21 and the foam collar 23 are designed so that onrelease from the cradle 13 the marker 11 floats to the surface in astable manner at a predetermined rate, typically 3 m/sec.

The hollow member 21 houses visual and audible pyrotechnics componentscomprising 3 flash filled ejectable noise pods 25 and a surface burningflare 27. The hollow member 21 also houses an ignition system 26 and atime delay fuse 28 for the pyrotechnics components. The ignition system26 and the time delay fuse 28 are designed so that the marker 11 reachesthe surface before initiating an expulsion charge which createssufficient internal pressure to shear the nose closure cap 29 and toeject the noise pods 25 upwardly into the air and to ignite the flare27.

The noise pods 25 are designed to ignite at a maximum height, typically4 meters, above the surface and to generate an audible noise, typically180 db of noise at 1 meter. The flare 27 is designed to burn for apredetermined time, typically 20 seconds, and to generate sufficient gasto prevent sea water extinguishing the event and to produce an intensitythat ensures visual recognition at distances of greater than 3 nauticalmiles under clear sunny day like conditions.

With further reference to FIG. 2, the severable coupling 37 comprises aband of reduced thickness in the rear end section 49 of the wall of thehollow member 21.

The rear end section 49 of the hollow member 21 and the base member 39define a watertight chamber 55 which houses an expandable bellows 59 anda pyrotechnic initiator cap 61, typically 1 watt/amp no fire. Theinitiator cap 61 is connected by means of a connector 63 to the firingsystem in the container 17. The assembly of the bellows 59 and initiatorcap 61 define the other part of the release means for severing thecouplings 37 between the markers 11 and the cradle 13.

In use, the SEM 7 and the visual indicator assembly 3 are deployed bycrane and sling from the deck of a ship onto the surface of the waterand are released to sink to the seabed. As the SEM 7 and the visualindicator assembly 3 fall through the sea the umbilical cord 5 betweenthe SEM 7 and the visual indicator assembly 3 drags the more positivelybuoyant visual indicator 3 well clear and to the rear of the sinking SEM7.

As the visual indicator assembly 3 sinks to a predetermined depth,typically 10 meters, the water pressure acting on the end of thecontainer 17 deforms the surface to initiate an internal micro-switch.The actuation of the micro-switch enables power from the battery pack inthe container 19 to be applied to the electronics components in thecontainer 17 and the visual indicator assembly 3 thereby becomes active.On the seabed the SEM 7 may become buried in mud with the visualindicator assembly 3 floating free of the surface conditions andtethered at a distance, typically 2 meters, from the SEM 7.

In order to conserve power and to enable the system to operate forprolonged periods unattended, typically 90 days, the visual indicatorassembly 3 is designed with a lower power consumption mode when it isnot active. In this condition the micro-controller in the container 17enters a "sleep" mode leaving only the first stage of the sonar receivercompletely awake.

When the SEM 7 detects the correct ship stimuli that induces the SEM 7to transmit through the water a "fired" code, typically consisting of aseries of 10 millisecond tone bursts, the inbuilt hydrophone in thecontainer 17 detects the initial tone burst, and the electronics modulesin the container 17 ignite the pyrotechnic initiator cap 61. The ignitedpyrotechnic composition generates sufficient gas to extend the bellows59 against the cradle 13 and thereby to apply a tensile force betweenthe marker 11 and the cradle 13 to shear the coupling 37 and thereby torelease the marker 11. The ignition of the pyrotechnic initiator cap 61also ignites the time delay fuse 28 and thereafter the ignition system26 for the visual and audible pyrotechnic components in the marker 11.

The preferred embodiment of the marker 11 is shown in FIG. 3 is similarto that shown in FIG. 2 and the like numerals denote like parts in thefigures.

The only difference between the two embodiments is that the assembly ofthe expandable bellows 59 in FIG. 2 is replaced by a piston assemblythat is positioned between the rear end 83 of the hollow member 21 andthe base member 39.

With reference to FIG. 3, the piston assembly comprises, a pistonhousing 91 which defines a piston chamber 93, and a piston 95 which isslidable in the piston chamber 93.

In use, when the electronics modules in the container 17 ignites thepyrotechnic initiator cap 61, the ignited pyrotechnic compositiongenerates sufficient gas to cause the piston 95 to slide forwardly inthe piston chamber 93 to apply a tensile force against the rear end 83of the hollow member 21 to shear the coupling 37 and thereby to releasethe marker 11.

The preferred embodiment of the marker 11 shown in FIG. 4 is similar tothat shown in FIG. 3 and like numerals denote like parts in the figures.

The main difference between the two embodiments is the construction ofthe forward ends of the markers 11. In this connection, in the preferredembodiment shown in FIG. 4 the hollow member 11 terminates in a hollowellipsoidal shell 99 which houses the pyrotechnic components and iscapable of sinking after ignition of the pyrotechnic components. In thisconnection, in order to facilitate recovery, each marker 11 may house atether (not shown) which is connected to the cradle 13 and dispensedwhen each marker 11 is released. The arrangement is preferableenvironmentally to the closed cell foam collar 23 of the preferredembodiment shown in FIG. 3.

The visual indicator assembly 3 described above with reference to thefigures is a convenient and reliable means for providing an almostimmediate visual and audible indication that a SEM has been detonated.

Many modifications may be made to the preferred embodiment describedabove without departing from the spirit and scope of the presentinvention.

We claim:
 1. A visual indicator assembly for use in underwaterapplications comprising:(a) a surface position marker comprising aforward section and a rear section, the forward section having abuoyancy means and the marker being adapted to provide visual and/oraudible indications on the surface; (b) a support means cooperating withthe rear section of the marker for supporting the marker underwater; (c)a severable coupling which couples together the forward section and therear section of the marker; and (d) a release means comprising anejection means for applying a tensile force between the forward sectionof the marker and the support means to sever the coupling and to releasethe forward section of the marker to float to the surface in response toa "fired" signal.
 2. The assembly defined in claim 1 wherein the markeris adapted to provide visual indications when it floats to the surface.3. The assembly defined in claim 1 wherein the marker is adapted toprovide visual and audible indications when it floats to the surface. 4.The assembly defined in claim 1 wherein the marker comprises visualand/or audible pyrotechnics components.
 5. The assembly defined in claim4 wherein the marker comprises an ignition system for the visual and/oraudible pyrotechnics components.
 6. The assembly defined in claim 1wherein the release means is responsive to a "fired" signal from aStonefish Exercise Mine.
 7. The assembly defined in claim 6 wherein the"fired" signal is a sonar signal.
 8. The assembly defined in claim 6wherein the release means comprises a means for receiving andrecognising the "fired" signal.
 9. The assembly defined in claim 1wherein the marker houses the ejection means.
 10. The assembly definedin claim 9 wherein the marker comprises a watertight compartment andthat the ejection means be located in the compartment.
 11. The assemblydefined in claim 9 wherein the ejection means is adapted to actuate theignition system for the visual and/or audible pyrotechnics components ofthe marker at the same time the ejection means applies the tensileforce.
 12. The assembly defined in claim 11, further comprising a delayfuse to delay ignition of the ignition system for the visual and/oraudible pyrotechnics components of the marker until the marker reachesthe surface.
 13. The assembly defined in claim 12 comprising:(a) aplurality of the markers; and (b) a plurality of the severablecouplings.
 14. The assembly defined in claim 13 wherein the releasemeans is operable to sever the couplings and to release the markerssuccessively in a predetermined sequence.
 15. In combination, the visualindicator assembly defined in claim 1 connected to a Stonefish ExerciseMine.